黄瓜腐霉菌苗期猝倒病致病机制研究

 本文明确了Pythium aphanidermatum主要靠生产以PG(多聚半乳糖醛酸酶)为主的一系列细胞壁降解酶的协调作用侵染黄瓜幼苗。植株胚轴细胞壁随苗龄增加,果胶物质增加最明显。病菌可在健胚轴及其细胞壁上培养产生果胶酶,其中细胞壁对PG的诱导作用比胚轴明显。随病菌致病力增强或病菌果胶酶浓度加大,胚轴的浸解和释放还原糖愈加明显。健株外渗物中虽也含有细胞壁降解酶,但比病菌的产生量少,活性低。病菌在寄生体内产生的细胞壁降解酶总酶活性,尤其是PG总酶活性与病菌致病力关系最为密切。这类细胞壁降解酶易受培养基成分和酸度的影响。经染色、显微及超微观察证实了该菌侵入黄瓜苗的机制是以酶解作用为主。     

腐霉对甲霜灵抗性测定及其生物防治

测定了腐霉属的8个种209个菌株对甲霜灵在浓度为0.5和50ug/ml时的抗性，从实验中观察到不同菌株对甲霜灵抗性变化的范围非常大，有95株在0.5ug/ml时，菌丝即停止生长，在20株在50ug/ml时，菌丝生长速度与对照几乎一样。经鉴定，这209株菌中，优势种为终极腐霉(Pythium ultimum）和刺腐霉(P.spinosum)。20株高抗菌中,P.ultimum占16株，P.irregulare占2株，P.spinosum和P.graminicola各占1株。盆栽试验表明：假单胞菌株Pseudomonas sp.CR56对高抗菌株P.ultimum ONCUR01引起黄瓜苗期猝倒病具有显著的防效，防效与甲霜灵和五氯硝基苯相比，达到极显著差异。     

淡紫褐链霉菌NBF715防控黄瓜猝倒病及其机制的初步研究

为明确淡紫褐链霉菌NBF715对黄瓜猝倒病的防控效果和抑菌机制,对其进行了对峙培养、抑菌活性、抑菌物质测定和盆栽防效测定。结果表明,对峙培养条件下NBF715对瓜果腐霉抑菌率为55.6%,无菌发酵液稀释10、25、50倍和100倍对瓜果腐霉抑菌率分别为84.1%、69.2%、47.8%和36.5%。光学显微镜和扫描电镜下观察,与对照相比,NBF715处理后瓜果腐霉菌丝发生扭曲、肿胀变形和消解。NBF715菌株能产生淀粉酶、纤维素酶、β-1,3-葡聚糖酶和嗜铁素。发酵液原液和稀释5倍发酵液浸种处理,对黄瓜猝倒病防效分别为97.1%和80.2%。NBF715菌株具有较好的生防应用前景。     

应用地衣芽孢杆菌和木霉防治基质栽培黄瓜苗期猝倒病

黄瓜苗期猝倒病（Ｐｙｔｈｉｕｍａｐｈａｎｉｄｅｒｍａｔｕｍ）属世界性病害,在深圳的基质栽培蔬菜上普遍发生,平均发病率为１０％左右。本文探讨应用地衣芽孢杆菌和木霉防治该病的效果。１试验材料和方法１．１供试材料黄瓜苗期猝倒病病原菌瓜果腐霉系从黄瓜病株分离...     

南方大棚蔬菜苗期猝倒病及其防治

南方地区冬春季节空气和土壤湿度都很大,尤其是塑料大棚内湿度多处于过饱和状态,非常适宜猝倒病的发生,一些菜农常因该病而损失惨重,从而,制约着南方地区大棚蔬菜的发展。一、症状猝倒病好发于蔬菜的幼苗阶段,发病初期茎基部呈水渍状,绕茎一周腐烂变软,随后病部缢...     

氟唑活化酯诱导黄瓜抗猝倒病及其对黄瓜苗期生理指标的影响

采用室内盆栽法,测定了5%氟唑活化酯(2,2,2-三氟乙基苯并[1,2,3]噻二唑-7-甲酸酯,FBT)乳油对黄瓜猝倒病的诱导抗病作用,同时测定了其分别以喷雾和灌根处理对黄瓜苗期生理指标的影响。结果表明:氟唑活化酯以有效成分25 mg/L,间隔期7 d喷雾施药3次,对黄瓜猝倒病的防效可达77.28%。氟唑活化酯以有效成分15、25和50 mg/L的剂量喷雾或灌根处理,对黄瓜苗期的株高、节间距、鲜重和干重均有不同程度的抑制作用;以有效成分15、25 mg/L的剂量喷雾或灌根处理,对黄瓜苗期茎粗和根冠比有促进作用,但50 mg/L的剂量处理则对茎粗和根冠比表现出抑制作用。试验表明,氟唑活化酯对黄瓜猝倒病有较好的诱导抗病作用,并对黄瓜苗期的生理指标有一定影响。     

作物苗期立枯病和猝倒病的识别及防治

立枯病和猝倒病是许多花卉、蔬菜、果树、林木等苗期的根部病害。采用种子育苗和扦插育苗都可发生此病。病害普遍而严重。两种病害发生规律相似,防治方法基本相同。一、症状识别立枯病在早期发生,可引起烂种。苗期发病,茎基产生椭圆形暗褐色病斑,病斑逐渐凹陷,当病斑...     

玉米茎腐病生物防治初步研究

本文报道了应用绿木霉（Trichodermavirlde）和细菌防治由瓜果腐霉菌和禾谷镰刀菌引起的玉米茎腐病。苗期盆栽试验表明，细菌拌种，木霉菌拌种和木霉菌穴施配合细菌拌种对两种病菌的防效较明显。在人工接菌土壤内，对腐霉菌防效最高达58.15％；对镰刀菌防效达56.25％。在自然病土中最高防效达100％。在田间试验中，细菌拌种和木霉菌拌种防效也相当明显。所有处理的植株均比未处理的高，增产明显。     

哈茨本霉菌3亿CFU/g可湿性粉剂对番茄立枯病和猝倒病防治效果

通过田间试验明确哈茨木霉菌3亿CFU/g可湿性粉剂对番茄立枯病与猝倒病的防治效果.结果表明,哈茨木霉菌3亿CFU/g可湿性粉剂能很好的防治番茄立枯病与猝倒病,在6～18亿CFU/m2(制剂用量2～6g/m2)使用剂量下,其对番茄立枯病防效达75％～86％左右,对番茄猝倒病防效达75％～85％左右,并且分别高于对照药剂多菌灵·福美双30％可湿性粉剂和霜霉威盐酸盐722g/L水剂.     

哈茨木霉菌3亿CFU/g可湿性粉剂对番茄立枯病和猝倒病防治效果

通过田间试验明确哈茨木霉菌3亿CFU/g可湿性粉剂对番茄立枯病与猝倒病的防治效果。结果表明,哈茨木霉菌3亿CFU/g可湿性粉剂能很好的防治番茄立枯病与猝倒病,在6~18亿CFU/m2(制剂用量2~6g/m2)使用剂量下,其对番茄立枯病防效达75%~86%左右,对番茄猝倒病防效达75%~85%左右,并且分别高于对照药剂多菌灵·福美双30%可湿性粉剂和霜霉威盐酸盐722g/L水剂。     

Biological control of damping-off caused byPythium ultimum andRhizoctonia solani usingTrichoderma spp. applied as industrial film coatings on seeds

Conidia of sevenTrichoderma strains were applied on cucumber or radish seeds as a simple methyl cellulose coating or through an industrial film coating process. The seeds were sown in a peat-based soil artificially infested byR. solani orP. ultimum. Four strains controlled damping-off caused byR. solani when applied as a simple coating or as an industrial film-coating. Also, four strains significantly reduced damping-off caused byP. ultimum in cucumber. A correlation was found between production of volatile antibiotics in vitro and control ofP. ultimum. Survival during storage varied according to the strain. Better survival was observed for two strains, with a decrease in conidial viability of one order of magnitude after storage for three and five months at 15 ° C and 4 ° C, respectively. The results show the feasibility of biocontrol of seedling diseases by some antagonists applied onto seeds through an industrial film-coating process.     

Effect of salinity on pythium damping-off of cucumber and on the tolerance of Pythium aphanidermatum

A study was conducted to investigate the effect of salinity on pythium damping-off and tolerance to salinity among Pythium aphanidermatum isolates from different geographical origins, genetic backgrounds and saline/non-saline soils. Increasing irrigation-water salinity from 0·01 to 5 dS m⁻¹ significantly increased mortality in cucumber seedlings inoculated with P. aphanidermatum and reduced dry weight of non-inoculated seedlings. In vitro tests in culture media amended with different concentrations of NaCl showed that growth of P. aphanidermatum, P. spinosum and P. splendens isolates was stimulated or unaffected at salinity levels stressful for cucumber (electrical conductivity = 5 dS m⁻¹). Significant differences were found in tolerance to salinity among 47 P. aphanidermatum isolates obtained from different greenhouses. The concentration of NaCl required to reduce growth of P. aphanidermatum isolates by 50% varied from 23 to 62 dS m⁻¹, with an average of 46 dS m⁻¹, however, oospore production was more sensitive to salinity and no oospores were produced above 20 dS m⁻¹. Analysis of tolerance of P. aphanidermatum isolates to salinity showed no relationship between tolerance to salinity and geographical origins or genetic data. Isolates of P. aphanidermatum from greenhouses with no salinity problems were as tolerant to salinity as isolates obtained from salinity-affected greenhouses, suggesting lack of evidence for ecological adaptation within P. aphanidermatum in Oman. Increased mortality in cucumber seedlings at higher salinity levels may imply a synergistic interaction between salinity stress and salinity-tolerant Pythium species on cucumber seedlings, resulting in greater seedling losses.     

Molecular characterization and pathogenicity of Pythium species associated with damping-off in greenhouse cucumber (Cucumis sativus) in Oman

A study was undertaken in 2004 and 2005 to characterize pathogens associated with damping-off of greenhouse-grown cucumber seedlings in 13 districts in Oman. Identification of Pythium to the species level was based on sequences of the internal transcribed spacer (ITS) of the ribosomal DNA. Of the 98 Pythium isolates collected during the survey, Pythium aphanidermatum , P. spinosum , P. splendens and P. oligandrum accounted for 76%, 22%, 1% and 1%, respectively. Pythium aphanidermatum was isolated from all of the districts, while P. spinosum was isolated from seven districts. Pathogenicity tests showed inter- and intraspecific variation in aggressiveness between Pythium species. Pythium aphanidermatum , P. spinosum and P. splendens were found to be highly aggressive at 25°C. However, the aggressiveness of P. spinosum decreased when the temperature was raised to 30°C, which was found to correspond to the lower frequency of isolation of P. spinosum in the warmer seasons, compared to the cooler time of the year. Pythium aphanidermatum exhibited limited intraspecific variation in the sequences of the ITS region of the rDNA and showed 100% similarity to the corresponding P. aphanidermatum sequences from GenBank. The ITS sequence data, as well as morphological characteristics of P. spinosum isolates, showed a high level of similarity within and between P. spinosum and P. kunmingense , and suggested that the two species were synonymous. This study represents the first report of P. spinosum, P. splendens and P. oligandrum in Oman.     

Suppression of pre- and postemergence damping-off in corn by Burkholderia cepacia

Burkholderia cepacia (syn. Pseudomonas cepacia) strain PHQM100 applied as a seed coating was tested in growth chamber experiments for its ability to suppress preemergence damping-off, and postemergence damping-off in corn induced by Pythium and Fusarium spp. The symptoms observed in bioassays with soils naturally infested with the fungal pathogens were seed rot with Pythium spp. and mesocotyl and root tissue necrosis in the presence of Fusarium spp. Three corn cultivars that differed in their susceptibility to damping-off pathogens were used. Cultivar L was susceptible to pre- and postemergence damping-off, whereas cv. LPDP and cv. LG11 were moderately resistant and resistant to the damping-off diseases respectively. In the presence of Pythium spp., seed treatment with B. cepacia reduced seed rot, as compared to the untreated seeds, and this reduction was more consistent in the cv. LPDP than in the resistant cv. LG11 or the susceptible cv. L. In soils infested with Fusarium spp., seed treatment significantly reduced root and mesocotyl necrosis as compared to the untreated seeds, and this reduction was more consistent in the resistant cultivars LG11 and LPDP than in the susceptible cv. L. Root colonization levels by B. cepacia were similar in the three corn cultivars tested. Biocontrol efficiency of B. cepacia varied among cultivars mainly due to the differences in their susceptibility to the fungal pathogens. In spite of variability and also irrespective of the soil characteristics, B. cepacia increased seedling emergence and decreased mesocotyl and root necrosis when used as a seed coating.     

木霉融合子Tpf-2的定殖及其对番茄防御酶系的影响

利用qPCR检测木霉融合子Tpf-2在番茄根际土中的定殖,并采用生理生化法测定Tpf-2对番茄叶片中相关防御酶活性的影响。结果表明,在整个番茄生育期内(0~150d),Tpf-2均可在番茄根际土中定殖,相对定殖数量随时间的延长呈下降趋势,同时接种木霉和瓜果腐霉处理组中Tpf-2相对定殖数量高于同期无病原菌处理组。不同处理组番茄叶片中的超氧化物歧化酶SOD、过氧化物酶POD及过氧化氢酶CAT的活性不同,同时接种木霉和瓜果腐霉处理组中上述3种酶活性增加显著,与只接种瓜果腐霉处理组间存在极显著性差异(P0.01)。综上可见,木霉融合子Tpf-2的厚垣孢子定殖周期长,定殖后可诱导番茄叶片中相关防御酶活性的提高,本研究为揭示其生防机理及菌株应用提供了科学依据。     

土传黄瓜立枯病高效拮抗菌的筛选鉴定及其生物效应

采用平板对峙法从黄瓜根际土壤中分离出的400余株细菌菌株中筛选出16株对立枯丝核菌Rhizoctonia solani具有拮抗效果的菌株,抑菌带直径在0.81～1.93 cm之间。并从中选出3株抑菌带直径在1.6cm以上的菌株N33、N35和N43,结合形态、生理生化特性及16S rDNA序列比对分析,鉴定N33菌株为假单胞菌属Pseudomonas sp.,N35和N43菌株为芽胞杆菌属Bacillus sp.。通过在黄瓜育苗基质中添加选育的高效拮抗菌株,观测其对黄瓜苗生长的促进作用以及对立枯病的防治作用,3株菌株均具有促进黄瓜苗期生长和防治苗期立枯病的作用,其中N43菌株促生及防病效果均最显著,地上部鲜重比对照处理增加62.16%,防治效果达62%。     

冷季型草坪腐霉猝倒和叶腐病的发生规律及防治技术

研究了冷季型草坪腐霉猝倒和叶腐病发生规律和防治技术，结果表明，苗期处于20-30℃、持续高温、-必植（3-5株/cm^2）等条件下最有利于腐霉病菌的侵害；腐霉猝倒和叶腐病发生同草坪播种期关系密切，湿热季节（4月上旬至8月下旬）播种严重受害，雨后积水可导致毁坪，防治该病要改善草坪基因条件，在上年10月下旬至当年3月上旬播种，用25%甲霜灵WP100倍液浸种，适当稀播，发病季节多次喷施甲霜灵或乙磷铝等针对性农药。     

玉米茎腐病病原菌检测方法研究

为提高玉米茎腐病病原菌检测结果的准确性和可信度,以组织分离法做对比,采用分子检测法,对采自田间的189个玉米茎腐病病株进行真菌种类的鉴定和数量的统计。结果表明,分子检测法对腐霉Pythiumspp.的检出频率为29.24%,对镰孢菌Fusariumspp.的检出频率为73.68%,组织分离法对腐霉的检出频率仅为0.58%,对镰孢菌的检出频率为60.82%,两方法的符合率最高仅为35.92%,最低为0。因此,采用组织分离和分子检测相结合的方法可提高玉米茎腐病病原菌鉴定结果的准确性。     

寡聚糖在农作物病害防治中应用研究

为研究寡聚糖在农作物病害防治中的作用机制(直接抑菌或诱导抗病)，采用生长速率法测定了寡聚糖与3种致病真菌的互作关系，结果表明，寡聚糖对3种病原菌均存在不同程度的抑制作用，EC50分别为：立枯丝核菌0．01％、腐霉菌0．1％、镰刀菌0．1％：从寡聚糖对3种离体病原菌的抑制程度来分析，它的田间病害防治中的应用价值，应归因于三方面的因素：它对病原菌的抑制作用、对农作物的生长调节作用及诱导植物抗病性。